I mean when was it broken? It kinda sucked in TBM, between aggro nerfs, shielding nerfs, rain nerfs, mana regen troubles, etc. But we were still pretty competent soloers during TBM, it just wasn't really enjoyable gameplay (at least for me). It's gotten a lot better since then, though.

Some of the improvements:

Empires of Kunark

Innate Defense - Pet EM Cloaks now come with an effect called "Innate Defense," which adds 1% mitigation per EM rank. The highest is 25% at EM 25. For reference, this is the same kind of mitigation warrior Last Stand uses (just 45% for that ability), so it's pretty effective (and always on, unlike Last Stand)

Avoidance Increase - Pet avoidance got a pretty significant increase during EoK. This brought avoidance levels closer to what they were in CotF relative to NPCs (they had fallen significantly during TBM/early EoK)

Theft of Essence Aura - Theft of Essence was turned into an aura and allowed to proc off of our "of Many" line. It increases swam pet attack significantly (and thus their DPS), but also increases evasion and HP for main pets and swarm pets.

Monster Summoning - Being able to reclaim MS was a massive increase to our sustainability in solo/group content mana-wise. This made our single target spells more viable because we had better ways to regain mana

Chaotic Fire/Firebound Orb - Both of these increased our DPS pretty significantly and made non-rain lineups much more viable. Chaotic Fire also helped with mana quite a bit.

Tome of Obulous - This is a smaller one, but it definitely does help reduce our aggro generation when pet tanking and it helps return mana.

Pet Swarm - You can now redirect your swarm pets via the /pet swarm command. This is really useful when soloing both to not waste RS pets and to have better control over RS pet offtanking.

Ring of Scale

Level Cap Increase - Obviously pets benefit significantly from level cap increases, and the 110 cap was no exception. The pets saw a really significant HP increase, as well as significant DPS increases. Overall the 110 pets are a pretty massive upgrade from the 105 pets.

Pet Spell Upgrades - In all honesty I don't like our pet heal and I don't use it much. That said, it, and quite a few of our other pet defensive/healing abilities got larger upgrades than most spells received.

Elemental Union Upgrades - Dzarn completely revamped Elemental Union, on top of significantly increasing the duration of Heart of Flames. Elemental Union now stacks and adds a ton of damage. This helps our burst DPS quite a bit.

Host of Elements Upgrades - This is a small one, but Host does way more damage and has way more health than it used to.

In fairness, content has gotten harder as well. RoS is tuned higher than EoK was in a relative sense (obviously things hit harder, but they are also tougher at 110 than EoK was at 105 for any class). At least to me, though, it feels like our solo capabilities are in a pretty good spot, regardless of the content. I've soloed in all of the RoS zones, including soloing the named in VP. In general, I think the class is a lot more fun to play than it was at 105.

If you're looking for power levels similar to RoF/CotF, then yeah, we aren't that good. Also if you mean "solo" in a very literal way as in without a merc, then you similarly are probably going to be disappointed. There are also classes more adept at soloing than we are (/wave Drogbaa). But in most cases we're in a pretty good place IMO.

When DB installed the pet nerfs from the issues players experience on the progression servers, on Live, it was quite disappointing when it became impossible to effectively solo while playing my magician.